package oj.day43;

import java.util.Scanner;

/**
 * 牛客网
 */
public class kotori和抽卡 {
    //没做出来,
    //看了答案刚开始没考虑到 tmp1和tmp2会越界.
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(),m = in.nextInt();
        double count = 0,tmp1 = 1.0,tmp2 = 1.0;
        for(int i = n-m+1;i <= n;i++) {
            //如果tmp1为int类型可能会越界
            tmp1 *= i;
        }
        for(int i = 2;i <= m;i++) {
            //如果tmp2为int类型可能会越界
            tmp2 *= i;
        }
        count = tmp1/tmp2;
        double result = count*1.0*Math.pow(0.8,m)*Math.pow(0.2,n-m);
        System.out.printf("%.4f",result);
    }
    //老师写法
    public void teacher() {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(),m = in.nextInt();
        double ret = 1.0;
        for(int i = n-m+1;i <= n;i++) {
            ret *= i;
        }
        for(int i = 2;i <= m;i++) {
            ret /= i;
        }
        for(int i = 1;i <= m;i++) {
            ret *= 0.8;
        }
        for(int i = 1;i <= n-m;i++) {
            ret *= 0.2;
        }
        System.out.printf("%.4f",ret);
    }
}
